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Experimental and Theoretical Study of the Combined Influence of Mechanical and Chemical Stress on Pit Initiation
Final rept. 1 Oct 2007-30 Sep 2010
WYOMING UNIV LARAMIE DEPT OF CHEMISTRY
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We have completed our work on modeling pit initiation and repassivation following mechanical pit initiation in a chemically aggressive solution. We created a new model combining all of the chemical processes that influence pit evolution including dioxygen reduction, field-assisted aluminum oxide film growth and chemical dissolution of the oxide film. All of these elements have never before been included in such a model. The model successfully fits pit repassivation under a range of conditions. A manuscript is submitted on this effort. We also used molecular dynamics simulations to explore the influence of strain on the coalescence of pits. We believe this mechanism may be the origin of the transition from metastable pits to stress corrosion cracking. The simulation has successfully shown pit coalescence as a function of strain under tension. A manuscript on this has been submitted.
APPROVED FOR PUBLIC RELEASE